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Allergic Reaction

Topic Overview

Allergies are an overreaction of the body's
natural defense system that helps fight infections (immune system).
The immune system normally protects the body from viruses and bacteria by
producing
antibodies to fight them. In an
allergic reaction, the immune system starts fighting
substances that are usually harmless (such as
dust mites, pollen, or a medicine) as though these
substances were trying to attack the body. This overreaction can cause a rash,
itchy eyes, a runny nose, trouble breathing, nausea, and diarrhea.

An allergic reaction may not occur the first time you are exposed to an
allergy-producing substance (allergen). For example, the first time
you are stung by a bee, you may have only pain and redness from the sting. If
you are stung again, you may have
hives or trouble breathing. This is caused by the
response of the immune system.

Many people will have some problem
with allergies or allergic reactions at some point in their lives. Allergic
reactions can range from mild and annoying to sudden and life-threatening. Most
allergic reactions are mild, and home treatment can relieve many of the
symptoms. An allergic reaction is more serious when severe allergic reaction
(anaphylaxis) occurs, when
allergies cause other problems (such as nosebleeds,
ear problems, wheezing, or coughing), or when home treatment doesn't
help.

Types of allergies

There are many types of allergies.
Some of the more common ones include:

Food allergies, which are more common
in children than adults. Food allergies are most common in people who have an
inherited tendency to develop allergic conditions. These people are more likely
to have asthma and other allergies. For more information, see the topic
Food Allergies.

Medicine allergies. Many prescription
and nonprescription medicines can cause an allergic reaction. Allergic
reactions are common and unpredictable. The seriousness of the allergic
reaction caused by a certain medicine will vary.

Allergies to insect venom. When you are stung by an
insect, poisons and other toxins in the insect's venom enter your skin. It is
normal to have some swelling, redness, pain, and itching at the site of a
sting. An allergic reaction to the sting occurs when your body's immune system
overreacts to the venom of stinging insects. For more information, see the
topic Allergies to Insect Stings.

Allergies to animals, which are more likely to cause breathing problems than skin
problems. You may be allergic to your pet's dead skin (dander), urine, dried
saliva, or hair.

Severe means that you are scratching so hard that your skin is cut or bleeding.

Yes

Severe itching

No

Severe itching

Has the itching interfered with sleeping or normal activities for more than 2 days?

Yes

Itching has disrupted sleep or normal activities for more than 2 days

No

Itching has disrupted sleep or normal activities for more than 2 days

Could you be having an allergic reaction to a medicine?

Almost any medicine can cause an allergic reaction. Think about whether the problem started soon after you began using a new medicine or a higher dose of a medicine.

Yes

Medicine may be causing allergic reaction

No

Medicine may be causing allergic reaction

Have your symptoms lasted longer than 2 weeks?

Yes

Symptoms for more than 2 weeks

No

Symptoms for more than 2 weeks

Many things can affect how your body responds to a symptom and what kind
of care you may need. These include:

Your age. Babies and older
adults tend to get sicker quicker.

Your overall health. If you have a condition such as diabetes, HIV, cancer, or heart
disease, you may need to pay closer attention to certain symptoms and seek care
sooner.

Medicines you take. Certain
medicines, herbal remedies, and supplements can cause symptoms or make them
worse.

Recent health events, such as surgery
or injury. These kinds of events can cause symptoms afterwards or make them
more serious.

Your health habits and lifestyle, such as eating and exercise habits, smoking, alcohol or drug
use, sexual history, and travel.

Symptoms of a severe allergic reaction
(anaphylaxis) may include:

The sudden appearance of raised, red areas (hives)
all over the body.

Rapid swelling of the throat, mouth, or tongue.

Trouble
breathing.

Passing out (losing consciousness). Or you may feel very lightheaded or suddenly feel weak, confused,
or restless.

A severe reaction can be life-threatening. If you have had a
bad allergic reaction to a substance before and are exposed to it again, treat
any symptoms as an emergency. Even if the symptoms are mild at first, they may
quickly become very severe.

Shock is a life-threatening condition that may quickly occur
after a sudden illness or injury.

Symptoms of shock (most of which will be present) include:

Passing out.

Feeling very dizzy or
lightheaded, like you may pass out.

Feeling very weak or having
trouble standing.

Not feeling alert or able to think clearly. You
may be confused, restless, fearful, or unable to respond to questions.

Shock is a life-threatening condition that may occur quickly
after a sudden illness or injury.

Symptoms of shock in a child may include:

Passing out.

Being very sleepy or hard
to wake up.

Not responding when being touched or talked to.

Breathing much faster than usual.

Acting confused.
The child may not know where he or she is.

Try Home Treatment

You have answered all the questions. Based on your answers, you may be
able to take care of this problem at home.

Try home treatment to relieve the
symptoms.

Call your doctor if symptoms get worse or you have any
concerns (for example, if symptoms are not getting better as you would expect).
You may need care sooner.

Allergies that are worse in damp weather. Mold may be the cause of allergies that get worse in damp
weather. Mold produces spores that move, like pollen, in outdoor air during
warmer months. During winter months, indoor molds can also be a
problem.

Indoor allergies. Newer, energy-saving homes that are
built with double- or triple-paned windows and more insulation keep heat and allergens indoors.

Prevention

To prevent problems with severe allergic
reactions:

If you or your child has had a severe allergic
reaction, talk to your doctor about getting a prescription for epinephrine. Learn how and when to give yourself an epinephrine shot, and have it
near you at all times.

If
you know you have an allergy to a medicine, be sure any new doctor knows about
your allergy before prescribing a medicine for you.

Ask your doctor if immunotherapy might help you. For this treatment, you get allergy shots or use pills that have a small amount of certain allergens in them. Your body "gets used to" the allergen, so you react less to it over time. This kind of treatment may help prevent or reduce some allergy symptoms.

Control exposure to outdoor allergens. Limit the
time you spend outside during allergy season. This may be the best approach to
controlling your symptoms. If you have a seasonal allergy:

During the peak of the pollen or mold season,
consider taking your vacation in a place that has fewer of these
substances.

Exercise regularly. Exercise produces adrenaline, a
natural way to relieve a stuffy nose. But exercising outdoors may also
expose you to more pollen or mold spores.

Control exposure to indoor allergens. Newer,
energy-saving homes built with double- or triple-paned windows and more
insulation keep
allergens and heat indoors.

Use an air conditioner or air purifier with a
high-efficiency particulate air (HEPA) filter.

Keep the house aired
out and dry. Keep the moisture level below 50%. Use a dehumidifier during humid
weather.

Dust and vacuum 1 to 2 times a week. Use a vacuum cleaner
with a HEPA filter, which collects dust-mite particles and pollen. Standard
paper bag filters may allow the stirred-up allergens to escape back into the
room.

Avoid carpet, upholstered furniture, and heavy drapes that
collect dust. Vacuuming doesn't pick up dust mites. Remove rugs and
wall-to-wall carpeting. Talk with your family about this measure and how this
will affect family life. Replace drapes and blinds with roll-down shades or
washable curtains.

Damp mop the floor once a day. Vacuum the walls,
ceiling, closet, and the backs of the furniture once a week to get rid of as
much dust as you can.

Use baking soda, mineral oil, club soda, or
vinegar to clean instead of using harsher cleaning solutions that can produce
allergic reactions.

Contact a pest control service, if necessary,
to get rid of cockroaches. Cockroaches and dead insects may provoke allergic
responses if you have allergic asthma.

Keep air
registers closed if there is a pet in the house. This will reduce the amount of
animal dander circulating in the house, especially in
the bedroom.

Repair any water-damaged areas from leaking roofs or
basements. These areas can be prime mold-growing areas.

Control exposure to animal dander (dead skin or scales from animals). Indoor pets can spread dander and other pet-related allergens such as urine and dried saliva throughout your home. Cats in particular spread dried saliva, but other small animals such as mice and gerbils can spread it too. Hair is often not the problem. Short-haired animals are no less of a problem than long-haired ones.

Keep the pet outside of the house or at least out
of the bedroom.

Bathe your pet once a week.

Ask a family member who does not have allergies to clean your pet's litter box.

Keep a caged pet, such as a gerbil, outside your home in a garage or shed.

Consider finding your pet a new home if your
symptoms are severe.

Be sure to tell your child's school staff about his
or her allergies. This is important so the school knows how to help your child
if he or she has an allergic reaction.

Breastfeeding may prevent allergies. Breastfeed your baby
for at least 6 months if possible to boost his or her immune system. Feeding
only breast milk during the first 6 months of life may reduce the chances that your
child will develop
food allergies or may decrease the severity of your
child's allergies. For more information, see the topic
Breastfeeding.

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